> > processes memory space. For older ISA cards that use page flipping you
> > could use a page fault trick to make it seem that the framebuffer is
> > linear when it isn't. Since the framebuffer window is 64K when the page
>
> This doesnt work. The DMA is direct, PCI DMA doesnt take page faults,
> only CPU's do that. For sane cards do overlay mode, for stupid cards you
> have to bounce the entire thing, you end up doing a two buffer
>
> grab1 write2 to fb with CPU
> grab2 write1 to fb with CPU
> repeat
>
> loop.
Oops. I should of addressed that in greater detail. I meant that for only
for the framebuffer. Since most video cards don't have OpenGL on chip it
would maximum performace if we allowed a process like a X client grab a
window in the framebuffer to draw directly into. Even if you set the
clipping rectangle on low end video cards so accel coomands will be draw
only in that rectangle a process can get around this by writing to the
framebuffer directly. Braindead yes but it does happen on alot of cards.
So set a hardware clipping rectangle. If you need to draw in the
framebuffer for software rendering the use this so you don't go off
rendering where you shouldn't.
> With ISA cards don't bother. You'll get 5-10fps at best even at low resolution.
> You'd be better off reverse engineering an old DOS era cards drivers and
> writing a feature connector mode card driver for something like the original
> full length hauppauge card
That was aimed at just fbdev. It would be nice if the current X server
for fbdev work on old paged isa cards without X code modification. Here we
don't care about high end graphics.
Their was discussion on the fbdev list also to be able to grab a window
for the video4linux guys. Any comments since youa re the one in charge of
this. What do you need from the fbdev guys to have video4linux work
together?
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